Aftmast rigs???

[Spiv]

Just happened across this quote from another subject thread this morning.

After 5y living aboard, crossing oceans, navigating passes and waterways, I could not agree more on that Brian, David has obviously been cruising too.

 

[brian eiland]

Failed Experiment

This posting was one I made over on another forum were I had posted several discussions of the 'Central Nacelle & Wave Splitter'. This gentleman SVNeko replied with this posting that hinted at becoming the 'guinea pig' for this nacelle concept as well as the aft mast concept.
http://www.cruisersforum.com/forums/f48/performance-50-55-cats-outremer-vs-catana-vs-swiss-catamaran-156934-2.html

Thanks for digging these up. Clearly you have thought about these issues in the past, as have others along the lines of the O Yachts solution. The O Yachts design seems to have adequately addressed the structural issues of having this "third" hull, and even taken advantage of it by designing in a mast aft rig supported by the nacelle and a carbon bulkhead (moving the rig aft is another design departure catching on slowly). The wave "attacking" nacelle seems to exist and work in powercat design. I wonder how it will function on a sailboat.

Part of the problem is getting a guinea pig to part with $1m to possibly end up owning a failed experiment. Would be nice to have some real world data on wave piercing nacelles on sailboats (as well as moving the rig slightly aft).

Could this 'failed experiment' be any worst than an older Prout design? These boats had a mast aft and a nacelle, neither of which, in execution, would I consider state of the art (they could have been better).

Yet a lot of owners are happy with these vessels, and they still resell in the market place.

I truly believe that my method of rigging my aftmast design will end up giving a far superior shape to those foresails than did the Prout rig.

 

[brian eiland]

Prout Rig Praise

http://www.cruisersforum.com/forums/f48/affect-of-mast-location-on-a-catamaran-21229.html#post226491

Sandy, I agree with your assessment of the earlier Prout 34's. As to what is commonly called the 'Prout' rig (cutter rig with mast stepped well aft by the companionway bulkhead), there have already been discussions of the relative merits of the rig in another thread on this site - I suspect it was in relation to some of the new Broadblue cats where there was a choice of rigs.

My Solaris Sunstream has an identical rig and I firmly believe that, for the following reasons, it has serious merit in an offshore cat:

1. It steps the mast at the strongest point of the bridgedeck - over the companionway bulkhead.

2. All lines are automatically led to the cockpit without various turning blocks for the halyards, reefing lines etc.

3. It allows sail area to be maintained, but breaks it up into smaller, and hence easier to handle sails. This is particularly important with respect to the mainsail, which will not require electric winches etc. to facilitate hoisting.

4. It has a dedicated stay for a staysail/storm jib, which brings the center of effort both down and back in precisely the wind conditions which favour the same (witness the number of offshore monohulls that now have 'solent rigs', with a detachable inner forestay for the staysail/storm jib).

5. The additional stays provide additional strength to the rig.

6. A furling staysail/storm jib permits the use of much heavier weight dacron than would be appropriate for a genoa, and therefore ensures that the lighter genoa is not used (abused) in excessive wind conditions. Furthermore, sail shape is easier to maintain if one is only reefing a furling sail to about 30 percent of its overall size. Finally, it is easier and safer to unfurl/reef a dedicated staysail/stormsail from the comfort of the cockpit than having to go forward to raise a sleeved storm jib ( eg. galerider) over the furled genoa, or to remove the genoa from the slot in the extrusion and raise a dedicated storm sail in its place. (On the negative side, I will agree that higher aspect-ratio sails tend to peform better and, in particular, the new huge mainsails with significant roach and flat-tops provide much more sail area up higher, where the winds tend to be stronger).

7. Since the Prout rig spreads the sail area more fore and aft than the typical fractional sloop rig, it will tend to have a lower mast. This in turn lowers both the center of effort and center of gravity, important in a catamaran in terms of reducing the risk of capsize. Furthermore, the lack of a mainsail with significant roach allows much better sail shape when reefed, and permits the use of backstays - further strengthening the rig.

Although direct comparisons are impossible without sailing the same hull with each type of rig, I have found that the larger foretriangle aids in tacking; I do not, for example, need to depower the main, as is sometimes necessary with huge flat - top mains in order to come about cleanly.

Once again, different horses for different courses - but for offshore sailing with its greater potential of being caught out in heavy conditions, the 'Prout rig' made and continues to make a good deal of sense.

Brad

 

[brian eiland]

Prout Rig Problem

...one 'less than optimal' feature...

...for a moment look at the profile drawing of my rig and picture it as though the mast was standing straight up vertically with its masthead in the same location as mine now is. Contrary to Tom’s statement, my forestays are really no longer than a conventional sloop rig, in fact they are likely shorter. And his comments about the angles between the backstay & the mast and the forestay & the mast are not quite correct. In reality it’s the horizontal (not vertical) component of the tension forces in these two stays that determines the ability of the rig to resist sag in the forestay……my masthead backstay has a more advantageous (rearward pulling) angle than does my forestay pulling forward. Interestingly, this phenomenon was probably most detrimental to the Prout mast-aft rig. Their short vertical mast at the aft position resulted in a highly sloped forestay that was both too long for the rig’s overall height, and it could over-exert a forward pulling force on the masthead that was indefensible by the shallow-angled backstays…..result, big time sag, sails too full. This rig had other problems as well….not an example of a successful mast-aft rig, but a case study in some things to avoid.

 

[brian eiland]

Hello brian. In your gallery there is a drawing of a single mast ketch. has anyone built one of these systems yet and are pics available.

I'm sorry Whitepointer, I forgot to get back to you. This subject thread is so long now it would take some time to go back and find each example of rigs that have experimented with this forwarded raked mast as I have suggested.

As a shortcut I might suggest that you go to google IMAGES and search for "aftmast". It will bring up a number of such project photos/dwgs, and you can inspect the link where they were posted by clicking on that box 'visit page'.

 

[tgtony52]

.........production boat would be several knots faster downwind than Wild Oats XI, Comanche and all the other 100 foot supermaxis........

Interesting to note that Comanche, which just won line honours in the 2015 Rolex Sydney Hobart Yacht Race, is an aft mast rig. Unfortunately Wild Oats XI had to retire, but was being led by Comanche at the time. Some details of Comanche's rigging were reported in Scuttlebutt Sailing News in Oct 2014 http://www.sailingscuttlebutt.com/2014/10/22/building-trust-comanche/

 

[CT249]

She's not an aft-mast rig in the sense that Brian's design is, though.

There's perfectly good reasons for moving rigs back and forth depending on other aspects of the design, but that doesn't mean that Brian's rig will achieve all the claimed advantages or that the conventional rig has the ills that are claimed.

My own yacht may possibly have its mast further aft than any other boat in its development class. I also sail a different class that is the only class in the world (I think) where the entire rig is moved back and forth during a race. Like Comanche it's just a matter of horses for courses, not one rig being generally better as is sometimes implied.

 

[Kojii]

Rig assessment article from wayback machine...
http://cruisenews.net/images/FastestRig1.jpg

Someone was questioning the real world examples of the Delta rig. There are two more pages.
The purpose of the "mastaft rig" is to establish space for clean luffs and lifting sail(s), not simply to put the mast aft. If you put the mast aft and don't use the space to change the sail rig from the standard conventional Marconi, I am not sure what the point is.

 

[CT249]

And we've had aerodynamic experts on here pointing out that there is no advantage to getting a clean luff, so that takes out another reason.

The article in the link should really be discarded altogether. The factual claims are so often incorrect. Even in the first paragraph it claims that rating rules favour bermudan rigs - that is simply not so. Just about all rating rules PENALISE the bermudan rig by requiring them to carry less sail (for the same rating) than non-bermudan rigs. The CCA rule, for example, allowed gaffers something like 12% more sail for the same rating - in no way is that discouraging gaff!

The second paragraph is equally misleading. It claims that rigs are not normally compared on similar hulls - but that completely ignores that many, many people did exactly that when the bermudan rig was first being adopted. An enormous number of individual boats were changed from gaff to bermudan - the entire Star class of the time, for example. The owners and sailors had direct personal experience of how the two rigs worked on the same hull - and overwhelmingly they chose the bermudan rig. And, of course, the fact that so many one design classes changed to bermudan confirms how silly it is to claim that the bermudan rig was chosen because of rating rules, which didn't apply to the one designs.

The third paragraph? Well, it's talking about what was proposed for third world fishermen, and that's not a subject I've researched. However, it gives no evidence for the claim that they were advised to shift to bermudan rigs.

The fourth paragraph contains another claim that either shows a complete lack of research, or a lack of honesty. This is the claim that there had never before been a test of two identical hulls, one with bermudan and one with alternative rigs. What a load of steaming rubbish. The very popular Stars did it. The very popular 12 Sq Metre Sharpies did it (and later stuck to gaff for their own reasons). The X Class (most popular racing yacht in England by some measurements) did it. Innumerable less popular one design classes also changed to bermudan rig after racing and trials. In the last few years the enormously popular Mirror has done it as well.

Every gaff development class also changed to bermudan, and while not all of them did tests on identical hulls, there was an enormous amount of testing on similar hulls. Much of this was under the full glare of publicity, over a wide range of conditions. They changed to bermudan because it went faster.

The article is nothing less than a blatantly arrogant insult to thousands of sailors who changed over to bermudan rigs for very good reasons that they understood because they were actually there, at the time, looking at the factors involved and deciding to change.

The same bizarre claim is repeated in the next paragraph. The final paragraph says that the sprit rig is faster - oh come on! It is apparent that the writers never thought to read about why sprit rigs were dumped by most sailors. They work in very specific situations, not in others. And most of the world's racing sailors learn on sprit rigs, so it's not as if they are ignorant of them. If the sprit rig was as fast as is claimed, the tens of thousands of Opti sailors and coaches would have noticed.

The other pages are just as bad. To show how wrong the article is, going from memory it effectively claims that if you took a beaten-up Hobie 16 off the beach and fitted it with a sprit rig made from an old tarpaulin, it would beat the world's best wing-masted carbon-kevlar 25' long hyper-performance C Class cats, and all the spinnaker-carrying highly tuned Tornado cats, around a track. So if the article is correct, the aerodynamic experts involved in cats are also drooling idiots who chose the wrong rig, too.

It's a terrible article that has so many fatal flaws that it should never have been published.

 

[Kojii]

You might want to tell the author, respectfully, just how foolish he is.

 

[gggGuest]

Tell the author - not the internet.

Its the Internet that needs to know, anyone who can write that garbage won't be told.

 

[Kojii]

Not very scientific lads...but very aggressive. This may be the group. You might find them open to different opinions. Anyhow, I think you disrespected their work, their actual experiment. They did an experiment. Made the effort. If you don't agree with their outcomes you could do the same experiment and publish your findings. That's how it's done.

https://en.wikipedia.org/wiki/Gifford_(company) They build some interesting stuff.

Respectfully

 

[CT249]

On the contrary, "we" (as in sailors) have been doing "the work" since 1800s - the experiment of sailing gaff v bermudan in comparable boats has been done countless times, and we've had lots of experience with sprit rigs. It was done in Long Island Sound, it was done in Tasmania, it was done on German lakes....it was done just about everywhere boats were raced.

When those thousands of experiments prove that bermudan rigs are normally faster, it is only reasonable to doubt the results of one poorly-described "experiment".

As far as being respectful, the author did not show any respect when he apparently assumed that the earlier sailors of the world were almost all too stupid to be able to assess what happened when they tried bermudan rigs instead of gaff and sprit. He also apparently believes that they are too stupid to be able to translate their experience in the world's most popular dinghy (which has a spritsail) to other classes.

Arguably, there is a fairly aggressive line of thought that holds that most sailors are stupid or hidebound when it comes to their rig and boat choice. It's hard to see why defending sailors against such attacks is seen as aggression.

As far as being "scientific", the article fails to follow many basic principles of scientific papers. It does not include the authors' names; it includes no information that could allow replication; it includes no lit review; it has apparently not been peer reviewed. I doubt whether any reviewer for a science journal would even accept it for review. Interestingly, although allegedly written for a university, it was not published in a journal. That is quite unusual given that building two boats and four rigs can't have been that cheap.

However, if the work is going to be looked at on its merits, can I ask a few questions?

1- How on earth can we be expected to believe a piece which makes the completely and utterly false claim that there have never before been tests of bermudan rig against other rigs on identical hulls?

As noted, there were many such, and they normally showed that bermudan was faster. Why you think the 19th and early 20th sailors normally changed from sprit rigs (which many of them knew well) to bermudan sloops, if the bermudan rig was slower?



2- If you (like the author) claim it was due to racing rules, please explain what ones. The author didn't, and there are few if any such rules.

3 - how can it be that the sprit rig is vastly faster, but all the people who design foiling Moths, foiling America's Cup class boats, offshore multis and skiffs are too ignorant to notice? That requires one to accept that various highly qualified aerodynamics experts are idiots.

Do you really think that the America's Cup rig designers are too stupid to know that they could have used a sprit rig and gone even faster?


4 - how can it be the sprit rig and gaff rig are vastly faster, when sprit rig and gaff rig classes are slower than comparable boats with bermudan rigs, as demonstrated by racecourses around the world?

Are the German Renjollen really stupid, when they rate the gaff rig boats as slower? Were the Canoe sailors who dumped the sprit rig really stupid too?


5 - if the tens of thousands of boats that changed from gaff rig to bermudan rigs all went slower, why did people kept on changing anyway? If the bermudan rig is slower, why did the people who were then when the changeover to bermudan occurred, like George Elder, "world" skiff champ Peter Mander, WP Stephens, Uffa Fox, Charles Nicholson, "Pim" van Hutschler, etc not notice?


6 - it's pretty easy for anyone in North America to prove the claims - borrow an Opti rig and put it on a Sunfish. According to the claims, the speed should increase so much that the Sunfish will blast past 505s, 29ers and Hobie 14s upwind. That will really wake people up!

7 - Why is it "aggressive" to point out issues with claims made by corporation? Should we just sit back and accept them?

 

[OzFred]

There is no date on the article to indicate it's age, however it might be worth noting that the Heron class allows either a Gunter (gaff) or Bermudan rig, the two have been racing against each other on otherwise identical boats for many years. The advantages and disadvantages of each have been mulled over for quite some time, I'm sure any long term Heron sailor can provide a thorough summary.

The gaff rigged Herons that I've seen sail with the gaff as close to the lower mast as possible, so that they are virtually Bermudan rigs.

Below is a photograph form their national championship published on the Australian class association site, I can only spot two gaff rigs:

So any claim that the performance of Bermudan and Gaff rigs has not been evaluated on otherwise identical boats seems to be no longer valid, if it ever was.

 

[sharpii2]

CT. Is it possible that the Bermudan rig is best for going up wind, which seems to be the most important point in racing?

I read in a post somewhere that much of racing now days is up wind and down wind, without much reaching.

Since I have never participated in an organized race in my life, I am quite ignorant on this matter.

It appears that the greatest gift of the Bermudan rig is its high aspect ratio, base on the formula: (Span^2)/Area.

In a race that is mostly upwind and down wind, a rig, such as this, could have a double advantage:

1.) upwind, its higher AR allows it to sail closer to the wind, and
2.) its taller mast (to get sufficient SA) allows for flying a bigger spinnaker.

I wonder if this is what some postors are referring as "the rules".

Not so much "design rules" but "race condition rules".

Are most races mostly upwind and down wind, distance wise?